1. Field of the Invention
The present invention relates to electrical cables and particularly to a gas feeder pipe assembly including electrical conductors. Such a pipe supplies a dry gas under pressure to a telecommunications cable to prevent moisture from penetrating the cable.
2. Discussion of the Prior Art
In the past, cables such as underground cables have been pressurized with a source of dry gas to prevent environmental moisture from permeating through the protective shields of such cables to adversely affect the electrical characteristics of electrical conductors within the cables. The dry gas is fed to the cables at various points along their paths to provide desired gas pressures throughout the lengths of the cables.
It has been realized that the use of dry gas can serve another important function to aid in providing quality communications lines. Aside from preventing the moisture from penetrating into the cables, gas pressure is used to monitor whether breaks in the shields of the cables exist. The gas pressure is measured at various stations along the lengths of the cables, and particularly at such stations where the gas is introduced into the cables. Pressure drops at the monitoring stations are indicative of defects in cable sheaths. Such defects can result in possible future troubles with communication lines within the cables in spite of the introduction of the dry gas. Preventive repairs can consequently be made on such cables during which time alternate communication routes are established without interruption of service.
Monitoring transducers transmit electrical signals indicative of gas pressures at the monitoring stations to central service stations. In accordance with prior art practice, conductor pairs in the communication cables are dedicated to transmit the signals from the transducer to the service stations. While monitoring the pressures has been found to be highly beneficial for maintaining the cables in good operating condition, conductor pairs are being lost to the transmission of telecommunication messages.
It is consequently desirable to free the dedicated conductor pairs of their function to transmit pressure information, and to thereby increase the capacity of the cables to transmit telecommunication messages.